AVAST, ME HEARTIES, `TIS TIME TO COME ABOARD FOR A NAP.

Byline: Susanne Hopkins Daily News Travel Editor

There is one thing that every bed-and-breakfast inn I have ever stayed in - good and bad, foreign and domestic - had in common: They were on solid ground.

Time for a change.

Which is what brings me to this red and black tugboat bobbing in the waters of Seattle's Lake Union. It's a b&b, but in this case, that stands for ``bunk and breakfast.''

The M.V. Challenger is a dressed-up old tugboat that has been welcoming guests for more than a decade.

``I think it's the only one in the country,'' says owner Jerry Brown, who acknowledges that there are other boats that welcome guests, but none are tugboats (although a man in Minneapolis is restoring one with the intent of opening it for overnight stays).

He grins. ``I know it's the only b&b in the country that's won (racing) trophies. It's probably the fastest b&b in the country.''

I suddenly envision myself at 2 in the morning aboard a b&b that is racing madly around Lake Union. Not a pretty picture.

But whether it's the only or the fastest tugboat b&b around, the M.V. Challenger is a funky place that kind of fits in with Seattle's quirky ambience - bold red and black inside and out, with a solarium, conversation pit, fireplace and entertainment center. It can sleep 18. (Brown also has two yachts available for rent for a total of 12 rooms.) The galley is always outfitted with fresh coffee, cookies and pretzels, and there are several shelves of videos for guests to choose from and watch on the boat's television.

My quarters are one of the original cabins, a two-bunk affair that is so small you have to go outside to change your mind (that's easy enough - there's also a bright red door that swings open to the deck). Handmade afghans cover the bunks and a teddy bear spreads its arms out in welcome. He holds an M.V. Challenger postcard and packages of M&Ms and peanut-butter-filled crackers. There's a wardrobe and lots of lights for reading. While I have a sink and a mirror, as well as a telephone and a radio, the head (we're talking shipboard lingo here) is down the passageway.

Ship rules are posted by the mirror in my cabin and they're pretty simple. The two most important are: no shoes allowed (you leave them by the front entry) and don't feed the cat - no matter how loudly she demands it. The cat is Tribble, a friendly gray tabby who becomes Chatty Cathy about suppertime.

Speaking of supper, there are plenty of restaurants around the lake and I take advantage of one of them. When I return, the moon is dancing on the rippling water, and I can see the lighted Space Needle just a comfortable walk away.

This is probably not, I can't help but think, what the sailors experienced on this tug. Built in 1944 for the Army Corps of Engineers, it was designed to sail the North Pacific and the Aleutian Islands, but it never got there. It spent time instead hauling cargo to Alaska. In 1985, Jerry Brown, a real estate appraiser and a restaurateur, bought it ``for fun.''

``It's been constant work for eight of the 11 years,'' he chuckles wryly. First, there was the conversion to a b&b, made somewhat easier because of the tug's configuration. ``This was built with all the cabins on the main deck or above,'' Brown says. Several of the cabins were opened up to accommodate queen-size beds; each has two exits. Overhead sprinklers were installed, and there are four security cameras on the boat - although not in private areas.

Now, it's a matter of maintenance - painting, redecorating, fixing. Brown and his wife, Buffy, live aboard. And with his restaurant background, Brown does much of the cooking. Breakfast is a vast repast served buffet style - fresh fruit, juice, coffee and tea, two egg dishes, one with seafood, pancakes, bacon, sausage and pound cake. Anyone who goes hungry here isn't paying attention.

Several of us cart our breakfast plates to the solarium, where on this Sunday morning, we look out at a still-gray world and an occasional kayak passing by. We talk about the boat, what a nice change it is and how it hardly seems to move.

``It wasn't what I expected,'' says one young woman, who was unsure she could sleep on a rocking boat.

She was not sleepless in Seattle.

B&B Basics Address: M.V. Challenger, 1001 Fairview Ave., Seattle, Wash. 98109.

Phone: [phone].

Price range: $59.51-$200 per night, double.

Number of rooms: 12 rooms on three boats, nine with private bath.

House rules: No smoking or shoes indoors; no pets; children by reservation only.

Money matters (credit cards, cancellation policy): Visa, MasterCard, American Express, Diners Club, Discover, personal checks, cash; entire reservation cost not refunded if cancellation is less than 14 days before stay (but a gift certificate good for a year is provided); full refund otherwise.

Check in/check out: 2-8 p.m. / 11 a.m.

Telephones, television: Televisions and VCRs in most of the rooms and the conversation area. Telephones in all rooms; fax available.

SOURCE: Daily News research

CAPTION(S):

2 Photos, Box

Photo: (1) Space is tight in this floating inn.

(2- -Color) The waters of Lake Union lull guests to sleep aboard the M.V. Challenger, a floating inn.

Susanne Hopkins/Daily News